fix: preserve toolArguments through normalization and activity state

- Add toolArguments to normalizeRunTimelineEvent output so persisted
  sessions retain tool argument data across app restarts
- Add toolArguments field to AgentActivityState and propagate it in
  applySessionEventActivity for real-time activity labels
- Add tests for normalization round-trip with and without toolArguments
- Add test for activity state including toolArguments

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/lib/sessionActivity.ts

@@ -7,6 +7,7 @@ export interface AgentActivityState {
   agentName: string;
   activityType?: SessionEventRecord['activityType'];
   toolName?: string;
+  toolArguments?: Record<string, unknown>;
 }
 
 export interface SessionUsageState {
@@ -45,6 +46,7 @@ export function applySessionEventActivity(
           agentName: event.agentName?.trim() || event.agentId?.trim() || agentKey,
           activityType: event.activityType,
           toolName: event.toolName,
+          toolArguments: event.toolArguments,
         },
       },
     };

src/shared/domain/runTimeline.ts

@@ -494,6 +494,7 @@ function normalizeRunTimelineEvent(
     targetAgentName: normalizeOptionalString(event.targetAgentName),
     toolName: normalizeOptionalString(event.toolName),
     toolCallId: normalizeOptionalString(event.toolCallId),
+    toolArguments: event.toolArguments,
     fileChanges: normalizeToolCallFileChanges(event.fileChanges),
     approvalId: normalizeOptionalString(event.approvalId),
     approvalKind: event.approvalKind,